DESCRIPTION: (Adapted from applicants abstract) Chromatin structural change plays a pivotal role in the regulation of gene transcription. Yet the molecular mechanisms of chromatin remodeling are not well understood. Eukaryotic DNA is packaged by wrapping around core histones to form nucleosomes and chromatin fiber. In order for the machinery of gene transcription to gain access to DNA, chromatin must undergo structural change, which is triggered by post-translational modifications on the histones. Recent yeast genetic and biochemical studies have led to the discovery of proteins and multi-protein complexes that act directly on chromatin to regulate transcription. Consonant with their essential roles in gene activation that controls numerous cellular processes, dysfunction of the chromatin-associated proteins has been implicated in various human diseases, particularly cancer. However, the specific function of many of these newly discovered proteins is poorly understood. The long term goal of this proposal is to develop an understanding of molecular mechanisms of chromatin remodeling and its role in gene activation. The approach is to focus on high-resolution structural and functional analysis of evolutionarily conserved protein modules found in chromatin-associated proteins. The recent structural and functional study by this laboratory of a histone-acetyltransferase (HAT) bromodomain showed that this highly conserved domain can specifically bind to acetyl-lysine on histones, providing the first evidence that bromodomains play a role in anchoring HATs and other co-activators onto active chromatin. Further investigations are proposed of ligand specificity of modules important for chromatin-mediated transcriptional activation, which include PHD finger (a zinc-binding protein) and SET domains. The specific aims are to determine three-dimensional structures using NMR, perform structure-based biochemical analysis to determine specificity of the modular domains, and develop high-affinity and selective peptide and non-peptide inhibitors of bromodomains, using a recently developed method for structure-based design of inhibitors by using NMR. It is expected that the results emerging from these studies will reveal new insights into the detailed molecular mechanisms used in chromatin remodeling and gene transcription, and could also lead to discovery of new drug targets for rational treatment of cancer.